RIM Material Selection

Determining which type of polyurethane material system will work best for an application will depend on the degree of rigidity is needed for the application. The degree of righty will place it one of two categories; a rigid polyurethane or an elastomeric.

A rigid polyurethane material system has a higher flexural modulus and degree of hardness. Typical properties associated with rigid polyurethanes are good chemical resistance, electrical properties and acoustical thermal insulation.

An elastomeric polyurethane material system is usually used in applications needing superior impact strength. They have good toughness and dimensional stability under a variety of temperature ranges (to -30 degrees Fahrenheit). Even under these temperature loads, the elastomeric polyurethanes retain excellent physical properties such as excellent abrasion, corrosion resistance and wear resistance.

Within these two categories (rigid and elastomeric) there are three (3) classifications of polyurethane (PUR) material systems; Solid PUR, Foamed PUR and structural composite PUR.

Thieme Corporation consistently molds the following polyurethane material systems:

Hard Sandwich Foam Used for RIM Molding

PUR Integral Hard Sandwich Foam (IHSF)

+ Sandwich-style design with high inherent rigidity
+ Extraordinary design flexibility
+ Good thermal and acoustic insulation properties
+ Used for thick and thin walled parts
+ Excellent surface finish
+ Structural design intent
+ UL 94 Rated V-0

Compact Foam Used for RIM Molding

PUR Compact Rigid Foam (Prism)

+ Compact structure and high impact strength
+ Mimics performance of injection molding type wall sections
+ Excellent stiffness to weight ratio
+ Good heat deflection temperature
+ Impact resistant Excellent surface quality for finishing
+ Parts as large as 10’ x 8’ x 3’ in a single shot
+ UL 94 Rated V-0

Casting System Used for RIM Molding

PUR Casting System (GS)

+ The material for mechanically and chemically stressed functional parts
+ Alternative to grey cast iron or steel
+ UL 94 Rated V-0

Flexible Foam Used for RIM Molding

PUR Flexible Rigid Foam (Flex)

+ High impact strength also at low temperatures extraordinarily durable
+ Aesthetics possible by means of structured tool surfaces
+ Excellent surface quality for finishing
+ Wide range of flexural moduli
+ UL 94 Rated HB

Energy Absorption Foam Used for RIM Molding

PUR Energy Absorption Semi Rigid Foam (EA)

+ Kinetic energy is converted into deformation energy
+ Can be optimally used for the most diverse requirements
+Low tendency for squeak and rattle
+ Passive passenger protection for all vehicle areas

Sound Absorbing Foam Used for RIM Molding

PUR Sound Absorbing Flexible Foam (SA)

+ Large Part Moldability and Backfilling
+ Can be used for the most diverse requirements
+ Exceptional sound absorption properties

Foamed Polyurethane Systems

  • Higher density skins with lower density microcellular cores in a sandwich like composition
  • Ability to design parts with variable wall sections (up to 2”) without sink or distortion in the part
  • Useful for load bearing applications
  • Allows designers to integrate the structure of a housing with the aesthetic needs of the part in a single part (sometimes eliminating the need for sheet metal sub assemblies for mounting the covers to)
  • Applications include but are not limited to business machine covers, medical device enclosures and housings, device bezels, ski’s, car spoilers and many more.

Solid Polyurethane Systems

Solid polyurethane systems don’t include blowing agents resulting in a solid rigid or elastomeric solid plastic. These elastomeric systems are typically used for automotive trims, fascias, bumpers and other parts in the construction, automotive, recreational and agricultural industries. The solid rigid systems are usually used to mold thin walled parts (3-6mm) resulting in applications such as business machine covers, medical device covers, large format parts and other parts similar in design and use as typical injection molded parts.

Structural Composite Polyurethane Systems

These systems are foamed systems and can variable wall sections. These systems have extremely high stiffness and high impact strength due to additives of glass or glass mats in the molding process. Typical applications include panels, shelves, load bearing parts and housings.